package com.pubinfo.passbook.common.utils;

import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;
import org.springframework.util.Base64Utils;

import javax.crypto.*;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * @author zhouch
 * @desc AES 加密工具类
 */
@Slf4j
public class AESUtil {
  
  private static final String KEY_ALGORITHM = "AES";
  private static final String DEFAULT_CIPHER_ALGORITHM = "AES/ECB/PKCS5Padding";//默认的加密算法
  
  /**
   * AES 加密操作
   *
   * @param content  待加密内容
   * @param password 加密密码
   * @return 返回Base64转码后的加密数据
   */
  public static String encrypt(String content, String password) {
    try {
      Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);// 创建密码器
      
      byte[] byteContent = content.getBytes(StandardCharsets.UTF_8);
      
      cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(password));// 初始化为加密模式的密码器
      
      byte[] result = cipher.doFinal(byteContent);// 加密
      
      return Base64Utils.encodeToString(result);//通过Base64转码返回
    } catch (Exception ex) {
      Logger.getLogger(AESUtil.class.getName()).log(Level.SEVERE, null, ex);
    }
    
    return null;
  }
  
  /**
   * AES 解密操作
   *
   * @param content
   * @param password
   * @return
   */
  public static String decrypt(String content, String password) {
    
    try {
      //实例化
      Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);
      
      //使用密钥初始化，设置为解密模式
      cipher.init(Cipher.DECRYPT_MODE, getSecretKey(password));
      
      //执行操作
      byte[] result = cipher.doFinal(Base64Utils.decodeFromString(content));
      
      return new String(result, StandardCharsets.UTF_8);
    } catch (Exception ex) {
      Logger.getLogger(AESUtil.class.getName()).log(Level.SEVERE, null, ex);
    }
    
    return null;
  }
  
  /**
   * 生成加密秘钥
   *
   * @return
   */
  private static SecretKeySpec getSecretKey(String password) {
    //返回生成指定算法密钥生成器的 KeyGenerator 对象
    KeyGenerator kg = null;
    try {
      kg = KeyGenerator.getInstance(KEY_ALGORITHM);
      //AES 要求密钥长度为 128
//            kg.init(128, new SecureRandom(password.getBytes()));
      SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
      secureRandom.setSeed(password.getBytes());
      kg.init(128, secureRandom);
      //生成一个密钥
      SecretKey secretKey = kg.generateKey();
      return new SecretKeySpec(secretKey.getEncoded(), KEY_ALGORITHM);// 转换为AES专用密钥
    } catch (NoSuchAlgorithmException ex) {
      Logger.getLogger(AESUtil.class.getName()).log(Level.SEVERE, null, ex);
    }
    return null;
  }
  
  /**
   * 复用类
   * (避免反复实例化)
   */
  public static class AESEncrytor {
    
    private Cipher cipher;
    
    private SecretKeySpec sks;
    
    /**
     * @param privateKey 密钥
     */
    public AESEncrytor(String privateKey) {
      try {
        cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);// 创建密码器
        
      } catch (NoSuchPaddingException | NoSuchAlgorithmException ex) {
        log.error("创建AES加密器错误: {}", ex.getMessage());
      }
      
      try {
        KeyGenerator kg = KeyGenerator.getInstance(KEY_ALGORITHM);
        // AES 要求密钥长度为 128
        // kg.init(128, new SecureRandom(password.getBytes()));
        SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG");
        secureRandom.setSeed(privateKey.getBytes());
        kg.init(128, secureRandom);
        //生成一个密钥
        SecretKey secretKey = kg.generateKey();
        sks = new SecretKeySpec(secretKey.getEncoded(), KEY_ALGORITHM);// 转换为AES专用密钥
      } catch (NoSuchAlgorithmException ex) {
        log.error(AESUtil.class.getName());
      }
    }
    
    /**
     * 加密
     *
     * @return
     */
    @SneakyThrows
    public String encrypt(String text) {
      
      cipher.init(Cipher.ENCRYPT_MODE, sks);// 初始化为加密模式的密码器
      
      byte[] result = cipher.doFinal(text.getBytes(StandardCharsets.UTF_8));// 加密
      
      return Base64Utils.encodeToString(result);//通过Base64转码返回
    }
    
    /**
     * 解密
     *
     * @return
     */
    @SneakyThrows
    public String decrypt(String encText) {
      //使用密钥初始化，设置为解密模式
      cipher.init(Cipher.DECRYPT_MODE, sks);
      
      //执行操作
      byte[] result = cipher.doFinal(Base64Utils.decodeFromString(encText));
      
      return new String(result, StandardCharsets.UTF_8);
    }
  }
  
}
